Dynamically generating flows with wildcard fields

Some embodiments of the invention provide a switching element that receives a packet and processes the packet by dynamically generating a flow entry with a set of wildcard fields. The switching element then caches the flow entry and processes any subsequent packets that have header values that match the flow entry's non-wildcard match fields. In generating the flow, the switching element initially wildcards some of all of match fields and generates a new flow entry by un-wildcarding each match field that was consulted or examined to generate the flow entry.